Source
Journal of Gerontology. 49(5):M227-33, 1994 Sep.
Abstract
BACKGROUND. Falls during walking are often triggered when a foot
contacts an obstacle in its path. Yet little is
known about the ability of individuals of any age to successfully
negotiate obstacles, especially under time-critical
conditions. METHODS. The gait of 24 young and 24 old healthy adults
(mean ages 23 and 73 years) was studied as
they approached and tried to avoid stepping on a band of light, not
knowing when or where it might appear on an 8
m-long walkway. This virtual obstacle was placed at the predicted
location of the next footfall with available response
times (ART) before heel strike that were varied randomly in 50 ms
increments from 200 to 450 ms. In addition, their gait
was observed as they stepped over a fixed virtual obstacle and over
an obstacle that appeared with approximately a
1000 ms ART. RESULTS. The old had an increased risk of obstacle
contact while negotiating obstacles under
time-critical conditions (p = .082). Mean rates-of-success (RS) in
obstacle avoidance for the young ranged from .205 at
a 200 ms ART to .969 at a .450 ms ART. Corresponding mean RS for the
old were .157 and .920. Lower extremity
simple reaction time (SRT) test made under static conditions showed
that the mean SRT of the old were approximately
80 ms longer than those of the young. Regression analyses suggested
that the old in fact would have needed only 30 ms
additional ART to achieve RS equal to that of the young for obstacles
appearing with ART from 300 to 450 ms.
CONCLUSIONS. Reductions in ART significantly decreased RS. Delays as
small as 50 or 100 ms in observing or
reacting to obstacles in real-life situations may significantly lower
the rate of success that subjects of any age have in
avoiding them. Age differences in SRT do not always reliably indicate
age differences in obstacle avoidance under
time-critical situations.